Although having wider application, the subject invention has particular utility for activating a pointer, cursor, or other on-screen symbol or element, such as an arrowhead, on a computer display. Use of the term "cursor" in the context of the subject invention needs clarification. The Computer Dictionary, Second Edition, 1994, by Microsoft Press defines a cursor as a blinking underline or rectangle, or a blinking vertical bar that marks the place where keystrokes appear when typed. This dictionary also recognizes that the term cursor or pointer may refer to the arrow or other on-screen icon that moves with movements of the mouse, and it is in this latter context that the term "cursor" is used herein.
Accurate and precise computer control with a cursor or pointer is of course necessary, and there are many devices available that provide such control. These known devices provide a direct, or touch-type, input to the computer for positioning and otherwise activating the mouse, they including the mouse, joystick, light pin, CRT touch screen and the keyboard. Such devices are very functional, but they rely on direct cable-connection to the computer.
Computer control without the such direct physical contact and cable connection, that is, touchless control, is also desirable and is known, but the systems that have been proposed have disadvantages that compromise the necessary accuracy and precision. These known systems involve computer-control by a user's finger or hand moving in free space apart from the computer. Examples of known touchless systems are disclosed in the U.S. Pats. Nos. 4,524,348 to Lefkowitz; 5,059,959 to Barry; and 5,288,078 to Capper et al.
The Lefkowitz apparatus relies on a user's hand to change the capacitance in a radio frequency oscillator to control the display. Thus, electrically inert objects will not be detected. Also, radio frequencies may require expensive components and may be subject to governmental restrictions.
The Capper et al. device uses IR emission, reflection and reception to provide an analog or on-off response to near-field objects. With multiple emitters, three coordinates of an object in free space can be generated. Although this apparatus avoids the expensive components of Lefkowitz and provides a response from most objects, it does not yield the accuracy and consistency necessary for most personal computers and other applications. Capper et al.'s reliance on light intensity to determine distances and the probable use of imperfect components are deficiencies. Dependence on light intensity will cause objects to have different reflective signatures, and imperfect components will cause movements of an object to be extenuated or attenuated so that only a relative position can be obtained. Moreover, the use of better components and the incorporation of lenses and special circuitry may still not solve these problems.
Barry's method and apparatus allow a user to position a cursor on the screen of a computer display by moving a finger in a field of transmitted signals of acoustic or electromagnetic energy. These signals reflect off the finger and return to receivers, similar to range-finding systems using sonar, radar or IR. The system determines the x, y coordinates of an object in space but not a z coordinate. Moreover, the disadvantages of high frequencies exist as discussed above.